Emacs is able to display Belarusian characters out of box in many
Linux distributions. However, the following conditions should satisfy:

Cyrillic iso-8859-5 fonts should be installed.

Emacs-mule package should be installed.

The user may want to change the default keyboard layout
("input method" in emacs slang) to jcuken. This
feature is provided by belarusian.el
along with some other goodies. Read the comments in the
beginning of belarusian.el for details
on the setup procedure.

After installing belarusian.el, you will
be able to switch the input method, by typing
C-\-cyrillic-belarusian-RET

For a more user-friendly setup, put the following lines in the
.emacs file: